1. Field of the Invention
The present invention relates to a method for detecting water in plastics using electromagnetic waves of a predetermined bandwidth and to a water removal system for plastic materials that implements the detecting method.
2. Description of Related Art
Generally, highly hygroscopic plastic materials for plastic molding are handled so as to avoid contact with air as much possible in performing molding and are removed of already-contained water by performing a heat treatment in a pre-feeding process. This is because when a molded product is molded using a moisture-absorbed plastic material as it is, an outer surface of the product becomes roughened or pores form due to a vaporization action of water attendant to heating. On the other hand, there are cases where a plastic must contain some amount of water from an aspect of product quality. That is, it is important to control a plastic to be in a favorable moisture state from a material stage to a product stage.
Conventionally, the amount of water in a plastic is generally measured by a Karl Fischer method. In comparison to a loss-on-drying method, with which a change in weight due to volatilization of water is measured, the Karl Fischer method enables detection of water specifically and is thus more accurate as a method for measuring the amount of water. As arts of measuring water by the Karl Fischer method, Patent Documents 1 and 2 are cited below.
Patent Document 1: Japanese Published Unexamined Patent Application No. H05-4716
Patent Document 2: Japanese Published Unexamined Patent Application No. H09-33484